Introduction

Windows Forms DataGrid as supplied supports two column types:

DataGridTextBoxColumn for editing Strings and

DataGridBoolColumn for editing Booleans.

Of course, the Windows Forms Library developers realized that this would not be sufficient, so they provided a base class (DataGridColumnStyle) that can be used to implement additional column types. This article discusses the enhancement of the DataGrid with new column types to allow the editing of a wide range of data types. The source for these enhancements is released to the public domain as part of the SekosPD.Windows.Forms library.

Demo Application

The screen grab above shows a simple demonstration application that allows the input of the contributors for a set of scientific fields. The DataSet schema is shown below. Each contributor has a photo column and a number of property columns for dates of birth and death and colour code.

To keep the sample simple, the data is persisted by writing the DataSet to disk as an XmlDocument. In a real application, DataSet changes would of course be persisted to a Data Tier - probably a database such as Microsoft SQL Server.

New Column Styles

For this demo, we'll be augmenting the column types with:

DataGridDataPictureColumn for editing Pictures and

DataGridPropertyEditorColumn for editing pretty well any other data type.

Because the AgileStudio product from which this code is derived is an add-in for Visual Studio, it is able to override the standard collection editor for ColumnStyles. Thus, the Add dropdown lists all the column styles available. Indeed, the designer is also overridden to allow columns to be added to a DataGrid with Drag and Drop.

Because the demo in this article is standalone, you will only see the two standard column styles in your editor and will have to manually add the appropriate code. (One way to do this is to add a standard DataGridTextBoxColumn and then change its type afterwards in the code window. Once you have done this, you will be able to change properties such as Mapping in the editor.) If you are interested in how to avoid this, let me know and I'll cover it in a subsequent article.

Editing Pictures

This is done by having a column of type DataGridDataPictureColumn. A right mouse click will bring up a context menu to allow the transfer of images via the clipboard or to allow the pasting of an image from a file.

Currently, ADO.NET only supports a small range of data types. For this reason, the picture field is encoded as base64Binary which is equivalent in .NET types to an array of byte. Internal functions ByteArrayToImage and ImageToByteArray handle the required conversions.

If you are using Microsoft SQL Server as your data tier, make sure you are handling base64 binary correctly. For example, if you are getting the data as XML, use a statement like the following:

SELECT ... FOR XML EXPLICIT,BINARY BASE64

Editing nearly any other Data Type

This is accomplished by having a column of type DataGirdPropertyEditorColumn. The DataGridPropertyEditorColumns in this example makes use of two editors - one for System.DateTime and one for System.Drawing.Color. Both these were implemented by Microsoft as DropDowns. This is the most common method, but editors for some types, for example, System.Drawing.Font, are implemented as Popup Dialogs.

The really nice thing is that there are dozens of UITypeEditors and TypeConverters included with .NET as standard. These are needed to drive the PropertyGrid that is used to edit properties in Visual Studio. You get to leverage all this functionality with almost no work. Just set the PropertyType property in your column as appropriate and everything else is automatic. It is also fairly easy to implement a TypeConverter and UITypeEditor for a type that you have written yourself.

There is one other property of DataGridPropertyEditorColumn that is important to mention: UseStringAsUnderlyingType. This should be set to true when binding to a DataSet if the type that you are binding is not one of the types supported by DataSet (For example, System.DateTime is supported, but System.Drawing.Color is not.) If you are binding to a different data source that does not have this restriction, you can always set UseStringAsUnderlyingType to false for more efficient data transfer.

Points of Interest

DataGridDataPictureColumn and DataGridPropertyEditorColumn employ DataPicture and PropertyEditor internally to handle a cell in edit mode. Both these controls can be used independently outside the DataGrid using standard simple data binding.

The source code for the SekosPD.Windows.Forms library is released to the public domain and is available here. Reference style documentation for the library source will be available here. You may also want to read the article "Edit Almost Anything - Part I", which examines other controls as well as the DataGrid.

The code released with this article is based on a portion of the AgileStudio product, which extends Visual Studio. Check out the free evaluation here which automatically maintains the datasets and SQL StoreProcs required for a specific user interface (for Windows or Web applications).

Conclusion

The code in this article is currently in VB.NET. If you would like a version in C#, let me know. I would also like to examine some of the really neat things that you can do with UITypeEditors including CollectionEditors to make the DataGridPropertyEditorColumn really fly. If you would like an article about this, get in touch.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

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About the Author

Declan Brennan is Chief Architect for Sekos Technology (www.sekos.com). Over the years he has worked in a huge range of technologies and environments and still gets a great thrill from the magic of computers.

When I tried it the conversion everything appeared to go OK without any errors.

The first problem I saw was trying to open form1.vb

"One or more errors encountered while loading the designer. The errors are listed below. Some errors can be fixed by rebuilding your project, while others may require code changes."

"The designer cannot process the code at line 160: Me.DataGridDataPictureColumn1.HeaderText = "Picture" The code within the method 'InitializeComponent' is generated by the designer and should not be manually modified. Please remove any changes and try opening the designer again."

I also got a lot of errors in the error window, but that was fixed by creating a reference to SekosPD.Windows.Forms in the project "DataGridSample" Somehow that reference seemed to be lost during the conversion to VS 2005

After making that change the project will compile and run.

However, it is not so easy to examine the structure when the Form designer won't display.

Hi-
Is there any possiblity to make Datagrid control (Winforms) column header sort arrow more prominent in .net 2003. In Windows forms Datagrid control, when user click on the column header, default sort arrow will appear but i want to replace it by another image or bitmap file. Is there any possiblity or any methods to override, so that we can place different arrow or image on the datagrid contol column header sort arrow look more prominent?

There are a couple issues if you use the DataGridPropertyEditor column to display a type whose Editor doesn't support painting. First, those columns displayed nothing. I traced it to what appears to be a missing "else" in the DrawData method of PropertyEditor - it seemed to me it should read

The underlying library is written in C#. It is just the demo that is written in VB.NET. The languages are very similar so you shouldn't have too many problems figuring out what is going on. If at some time in the future, I get the time to convert the demo to C#, I will of course post it on Code Project.

When producing your select statement make sure you append "FOR BINARY BASE 64". For example, try the free download of AgileStudio from www.sekos.com and look at the store procs it automatically generates. There are also subtleties in Data Set schema production and updating rows in SqlServer that are handled automatically among many other things.